Thanks for the question. I had the same issue and it seems that it was a simple solution. The order in which email addresses pop up seems to be impacted by the order (top to bottom) in which the address are listed in the 'Contacts' area. Check to see that the contact information is up to date and in the order you prefer and then when you compose a new email it should populate the email addresses when you type the person's name. Hope this helps!

Move the email address from the Email field in the form for that Contact to the Notes field. This way you can preserve the old email address and Gmail will not show it in the auto-population list. The contact will also show up when you search.

This doesn't answer the question (or I may have misunderstood something). OP doesn't want to add the old email. He wants to keep it but he wants to choose which one will appear first when composing an email
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JMaxAug 9 '12 at 12:27